The present invention relates to a multiple-use pressure-sensitive transfer recording media. More particularly, it relates to a multiple-use pressure-sensitive transfer recording media for use in over-strike or multi-strike on impact type typewriters or printers.
In multi-strike operation, a recording media is advanced by a pitch of substantially the same as or somewhat longer than the character width with each strike and the direction of the travel of the recording media is switched upon each passage of the full length of the recording media. During a plurality of passes of the recording media, the same position thereof is struck plural times by the typeface or the like.
In over-strike operation, a recording media is advanced by a pitch of shorter than the character width, for instance, 1/5 of the character width, with each strike, so that a portion of each strike is effected over regions which have been previously struck and the same position of the recording media receives a plurality of impacts during a single pass. The recording media is discarded after only a single pass.
Such multiple-use pressure-sensitive transfer recording media which have been known heretofore include a recording media which comprises a foundation and a finely porous layer on the foundation, the porous layer being composed of minute porous particles and a binder material for bonding the porous particles to each other, and containing a liquid ink paste incompatible with the binder material (See U.S. Pat. No. 4,515,489).
In the case of conventional multiple-use pressure-sensitive transfer recording media of this type, it has been recognized that a liquid ink paste having a high viscosity of more than a certain value (4,000 cP) must be used. The reason therefor is that if a liquid ink paste having a lower viscosity is used to reduce the amount of the liquid ink paste remaining in the porous layer after repeated use of the same position of the recording media, which probably improves the over-strike or multi-strike capability, the ink paste penetrates readily into a receiving paper, which results in pale coloration or low optical density of the image and the distortion of the image due to spread or blot of the ink.
When a liquid ink paste having such a high viscosity is used, the coloration of the image obtained in the initial strike is improved, but the lowering of the optical density of the image is sharp and the unevenness of the image is marked with increasing number of strikes in the same position of the recording media, so that the number of times that the same position of the recording media can be used in continuous strikes is upmost 10.
Moreover, in the case of the above-mentioned multiple-use pressure-sensitive transfer recording media, the lowering of the optical density of the image with increasing number of strikes in the same position is less sharp than that in the case of a conventional multiple-use pressure-sensitive transfer recording media wherein no porous particles are used, whereby providing a better over-strike or multi-strike capability. However, the finely porous layer is readily broken upon impact of the typeface or the like so that portions of the porous layer are transferred to a receiving paper together with the liquid ink, which causes dark spots or stains in the image. An attempt wherein an adhesive layer is interposed between the foundation and the porous layer has been made, but the above drawback cannot be overcome even by such attempt.
It is an object of the present invention to provide a multiple-use pressure-sensitive transfer recording media which is capable of giving sharp and clear images without any unevenness for a multiplicity of strikes at the same position of the recording media and the same position of which can be used many times for transferring the ink onto a receiving paper.
Another object of the invention is to provide a multiple-use pressure-sensitive transfer recording media which has a finely porous layer which is not readily broken by impact upon repeated strikes at the same position and the same position of which can be used many times for transferring the ink onto a receiving paper.
Still another object of the invention is to provide a multiple-use pressure-sensitive transfer recording media which has both advantages mentioned above.
These and other objects of the invention will become apparent from the description hereinafter.